Joining assembly for wave guide sections or the like



S. E. MILLER Oct. 3, 1961 JOINING ASSEMBLY FOR WAVE GUIDE SECTIONS 0R THE LIKE Filed Dec. 19, 1958 /NVE/vron S. E. M/L LER A 7` TORNEV IOINING ASSEMBLY' FOR WAVE GUIDE SECTIONS OR THE LIKE StewartE. Miller, Middletown, NJ.,"nssignor'tollellV This invention relates to the -'art of connecting sections of wave transmission line such as wave guides and, more particularly, to ymethods and. apparatuslffor aligning, coupling, `and joining sections-of` such lines.

It is well known that sections of wave guide, and particularly those-having circular cross sections lin planes transverse tothe direction" of energy propagation therethrough, may be joined byproviding the proper screw threads at'the ends'of keach section. Alternatively, each section of wave guide may be manufactured with an' integrally connected flange memberat each of its ends for connection toV a similar ange member of a succeeding section. The production of either iianges or 'screw threads, with their attendant close tolerances, adds considerably to the cost of wave 'guideapparatus. When the use ofrlong sections'of semipermanently continuous transmission line is contemplated, as in a long distance justifiable.r

United Statesl Patent, O

I, 3,003,020 'Patented .0st-

In the drawing: t

FIG. l is a longitudinal cross'sectional view of two wave transmission lines' jointed in'v accordance with the .Accordingly it is an objectof the present invention toy join successive lengths of wave transmission line more economically than heretofore.

Q A .more specific object istorjoin lengths ofv wave transmissionline by t-hermosetting a sleeve` surrounding 4the ends to be joined comprising layers of a continuous conductive medium interleavedwith dielectric bonding layers, the thermosetting being effected through heating the sleeve by passing electricrcurrent lfrom an external source through the conductive medium.

In accordance with the invention, the guidesr to be joined are suitably butted and aligned and are then wrapped in the vicinity of their butted ends with alternate layers of conductive material and dielectric material. The interleaved conductive and dielectric layers are impregnated with a plastic resin'or otherA material of thek v with a substantial portion of the mechanical strength `0f the sleeve being provided by its conductive layers.

A feature of *theV invention is, therefore, the duality of purpose associated in such an embodiment with the conductive layers of the sleeve in serving two distinct functions. First, these conductive layers provide the path through which the heating current ows and serve as the heating element in the thermosetting process and second, they impart mechanical strength tothe joint after `the thermosetting process is completed.

The `above and other objects, the nature of Ithe present invention, its other features and advantages will appear more fully upon consideration of the'speciic illustrative embodiments shown in the accompanying drawing'and described in detail below.

present invention;` Y t 1 FIG. 2 is a partially brokenaway perspective view of a helix waveguide embodiment of theinvention; and

FIG.k 3 is a perspective view of a further application of the principles of the invention. i

Referring now more particularly tothe'drawing, FIG. 1 shows an end portion of a first wavetransmission line or guide 11, assumed to be of circular transverse cross section, which is4 to be joined to van end'portion of a second wave transmission line or guide 12 of similar cross section. 'Inserted the end v`portions of the guides to be joined is removable aligning mandrel '13. Mandrel 13 has an outside'diameter'slightly less than the inside diameter of guides 11, 12.` This slight clearance not only facilitatesinsertion of Ithe mandrel but allows yfor anythermal expansion `of the mandrel of greater degree t-han'thel thermal expansion of guides 11, 12. Attached vto mandrel 13 by means of threads 24 is rod 15 which serves to permitI the insertion of mandrel 13 into the guides to lbe joined,"to permit its positioning llongitudinally at the junction 14 between the guides, and to permit its withdrawal after completion of the joining operation. Rod 15, therefore, has length greater than that of the glide section to be joined through which it is inserted. L

Guides 11, 12 are surrounded in 'the vicinity of their end portions by sleeve 16. Asillustrated in the cross sectional view of FIG.A 1, sleeve 16 comprises alternate layers of material of different compositionif Proceeding radially outward from the guide walls, dielectric? layer 17 is first encountered, followed by conductive layer 18, andthen alternately byiother dielectric layers 17 and conductive layers 18. The conductive medium of which conductive rlayers 18'are a part is, in accordance with the present invention, a continuous element. That is, the conductive medium isf'wrapped around thewave guide ends and interleaved with the dielectric material in a continuous spiral outward from .the guide surfaces. The conductive medium therefore yprovides, between its radially innermost and radially outermostr layers,-a spiral path for directand low'fr'equency electriccurrents introduced at one of these layers andf received at the other.

v According to the principles "of the. present invention,

current owing in the spiral conductive-medium is'intended to be partially converted, through ohmic` resistance losses, `intoheat energy and thereby raise the temperature of the sleeve'itsclf. It is not necessary," however, that the ohmic resistance of the conductive? medium be high. The major consideration in` selectinguthe material for conductive layers 18-is .mechanicall strength. Thus, for example, ordinarylgalvanized meshscreening would be suitable for use as thelconductiveifmedium ofthe sleeve 16. In such a case, a Ahigh current passed through the screening at low terminal voltage would elevatethe sleeve temperature Vsuiiciently to effect the" thermosettng process .Y e l The ldielectric layers 17, in additionto insulating adjacent conductive layers 18 from one another andffrom the conductive guides 11,12, serve as the very important bonding and heat` curing mechanism through which the guides semipermanently.

In FIG. l, current source 19 is attached to sleeve 16 at terminals 2'2, 23 through conductors 20, 21. vTerminal Z2 is attached to the spiral conductive member. of sleeve i5 at its inner extremity with respect to the. guides 1i, 12, While terminal Z3 is attached-to the conductive spiral at its outer extremity. .'Ihuscurrentsupplied by source 19 whichenters sleeve 16 via conductor 20 will be constrained to ow spirallythroughthe conductive wrapping member and be receivedtfby sourcel via conductor 2i. Terminals 2,2, 23 [allow-easy .Connection land disconnection of source 19 and sleevel.

In accordance with a preferred method of practicing the invention, guides 11 4,and 12 are approximately aligned before mandrel 13 is inserted. The mandrel is then properly positionedat the end portions to be joined and these end portionsaretightly wrapped with alternate .Layers of conductive screening and plastic resin impregnated fiberglass cloth. In order to prevent the short circuiting of the heating current to be `applied after wrapping is completed, the sleeve should be .wound such `that an insulating layer-.of 4liberglass separates the iirst conductive layer. from the guide Surfaces. it is convenient vfor the screening and the glass cloth to be wound around the guides simultaneously from continuous rolls and, therefore, the plastic resin may be suitably applied between turns as the kwinding progresses. Plastic resins suitable ffor application in the kpresent invention include epoxide resins Vof thetype Athat may be catalytically cured to form a thermosetting polymer. Terminal 22 may be created by placing `a conductive member longitudinally with respect vto the guides in contact with the screening Within the rst wrapping layer. A soldered connection between ,the conductive member. and the `screening may be provided if desired. The conductive member is permitted to extend beyond the sleeve at one end and this extension becomesterminal 22 for the connection of the external current source 19. "Ihewrapping is continued until the sleeve 16has the required radial thickness.

VThis thickness is determined by the desirability of having the bending stiffness of the Ysleeve at least as great as the bending stillness ofthe vsolid-wall metallic guides joined by the sleeve in order that uniform deformation of the semi-permanently connected Vwave guidesections be experienced when subjected tobending forces. Otherwise, a concentrated `bend would occur at `the joint. When the sleeve has reached the desired thickness, wrapping is discontinued, again positioning a conductive vmember in contact with` the outer conductive layer and permitting it to extend beyond Vthe sleeve at one end to form terminal 23. The outer layer of the sleeve, like the inner layer, should comprise insulating material to Vprevent short `circuiting problems.V Accordingly, the berglass wrapping materialrmay be continued for several turns after the conductive material-has been terminated.

When construction of sleeve `16 is complete, an electrical source -is connected'between terminals `22, k23. Ohmic `resistance presented toV electriccurrent owing from the source 19 through the conductive layers of sleeve 16 will `cause 'its temperature to rise. The length of time and degree of heat necessary for thermosetting depends upon Athe particular plastic resin chosen. As a specific example, galvanizedmesh screening may be utilized as the conductive medium VandShell-Chemical Corporations Epon 8l5\with curing agent T may be utilized as the bonding or dielectric layers. The temperature of `the sleeve should `then be raised to a level of the order of 200 degrees. Fahrenheit to accomplish thermosetting. It should vbe `notedthat if the material of mandrel l`13 `is selected to have a :thermalcoeilcient of expansion ygreater' :than Vthat-of the -material of `the guides tofbe joined, the 4heating processwill .cause mandrel 13` to ex- `Pied.lightly agaiusttheiriuside surfaces and tot .align their end portions precisely. This result will be achieved if, for example, the guides 11, 12 comprise copper and mandrel 13 comprises au aluminum alloy. Such a precise alignment is desirable in order that the butted wave guide ends present vassmall an impedance discontinuity to propagating wave energy as possible.

When the thermosetting process is completed the current source is disconnected from the terminals22, 23 and the sleeve is allowed to cool. Mandrel 13 is removed after it has cooled and has shrunk away from the inside surfaces of guides 11, 12. As a result of the thermosetting process, the conductive `layers of screening which served during the assembly process; as conductors of electrical current [and Yas heaters are laminated tightly with the glass clothv layers yand are tightly bonded ythereto with the polymerized resin. These conductive layers, theretore, forma mechanical component part of the cured joining sleeve and impart considerable strength to it. kA laminated sleeve unit containingran .interleaved mechanical strengthening member in accordance with the present invention isqconsiderably moregdurable and stronger per unit radial thickness than laminated joining units not including the ,metallic medium. An additional advantage offered by `the present Yinvention, Y especially attractive from a practical viewpoint, is the relative ease with which the heating vand thermosetting operations may be carried out Iby persons involved in installing and joining wave guide sections in actualeld operations.

FlG. 2 illustrates a joining assemblyin accordance with the invention as applied .to helix type wave guides. Illustrated are butted andy `aligned endportions of helix guides 31, 32 surrounded by sleeve 33 including laminated conductive layers 38 and dielectric bonding layers 39. Helix guides 31, lcomprise ,tightlywound helix 34, with adjacent turns insulated from each other by, for example, insulating coating 35 on the wires of the helix. Surrounding the helix -isv jacket 36 `which dissipates electric field components propagating therein. Dissipative jacket 36 is encased in outer jacket 37 which may be a conductive pipe comprising,forV example, steel 4or copper or which may bea Ynonconductivesheath comprising layers of glass cloth, or fiberglass, laminated together. The present invention is adapted to joining sections of helix wave guide of leither construction. The helix-type wave guide offers many advantages .over ordinary hollow conductive pipe for the transmission ofV energy in the circular electric or TEM mode configuration. Since the TEM mode is also attractive for longdistance high frequency transmission, the desirability of having an economical means of joining lsections of helix wave guide during installation of long distance helix wave guide connecting links between terminal points or repeater stations is obvious. The `details of the application of the present invention to helix-type Wave guides is substantially identical to that described above in connection with the hollow pipe wave guide embodiment of FIG. l.

FIG. 3 illustrates an application ofthe principles of the present invention to wave guides of non-.circular transverse cross section. .Speciically, in FIG. 3 the end portions of guides 41, .42 of rectangular transverse cross section are joined by sleeve 43 `which .is built up and thermoset in accordance .withthe principles of the present invention as described above.

in installations -in which the semipermanently continuous guide is to besubjected to highly corrosive surroundings or to destructiveinsects, it may be advisable to encase the entirelaminated sleeve in ajacket of lead or other material which is impervious to such `external inlluences.

In all cases it is understood that the above-described arrangements are illustrative -of a small number of the many specific Jemlmdiments -Nvhich could represent an application of the principles .of the invention. Other arrangements can readily be devised in accordance `with these principles by those skilled in the art without depart-y ing from the spirit and scope of the invention.

What is claimed is:

, 1. A long length of semipermanently continuous transmission line comprising a plurality of sections of transmission line having lengths which are short rrelative to said long length, said sections being mechanically coupled substantially solely by sleeves surrounding the abutted end portions of each of said sections comprising a plurality of interleaved conductive and dielectric Vlayers bonded with a thermoset resin, said conductive layers forming a continuous spiral conducting path for low frequency electric current introduced at one end of said spiral path and received at the other end of said path.

2. The method of semipermanently joining two lengths of hollow wave transmission line comprising the steps of placing `an insert within the en cl portion of each of said two lengths -to be joined to, align said portions, wrapping said end portions a plurality of times in overlaying spiral fashion with a continuous conductive medium and simul- 4 taneously interposing a dielectric medium impregnated with a plastic resin between each layer of said spiral conductive medium, passing an electric current through said continuous conductive medium for a time to elevatethe temperature of and to cure said plastic resin, andre-V moving said insert. t

3. A sleeve for joining the abutted end portions of transmission line sections comprising a plurality of alternate layers of conductive and dielectric media to be disposed over said end portions, said layers overlaying each Y other, said conductive media forming a continuously conductiveV spiral path for low frequency current between the innermost and the outermost ones of said conductive layers, said dielectric layers being impregnated with va thermosetting resin, and means for passing said current through said spiral path for a time to elevate the internal temperature of said sleeve, said conductive layers being adapted to remain in place to provide mechanical strength to `said sleeve after thermosetting is completed.

References Cited inthe file of this patent UNITED STATES PATENTS 2,340,926 Bradley Feb. 8, 1944 2,495,167 Horstman et al. Jan. 17, 1950 2,695,853 y Foreit Nov. 30, 1954 2,719,274 Luhrs Sept. 27, 1955 2,795,523 Cobb etal June 11, 1957 2,797,394k Clogston June 25, 1957 FOREIGN PATENTS Y t 120,846 Australia Jan. l0. 1946 217,080 Australia Nov. 15, 1956 502,328

Italy e Mar. 1956v 

